The preparation of polyhydroxy fatty acid amide surfactants by the reaction of fatty esters with N-alkylamino polyols is of considerable commercial interest. However, the resulting N-alkylamido polyol reaction products, such as the fatty acid N-methyl glucamides, are often contaminated with residual nascent sources of fatty acids. Contamination by such materials may be tolerable if the user can afford to purify the polyhydroxy fatty acid amides prior to use. Or, as a possible alternative, the user presumably could arrange for special care to be taken during the reaction in order to minimize the levels of nascent sources of fatty acids. However, the manufacturer of high volume, low-cost chemicals such as detersive surfactants can ill-afford special handling techniques or materials which require expensive purification steps. For example, the manufacturer of high sudsing detergent compositions which contain polyhydroxy fatty acid amide surfactants (e.g., C.sub.8 -C.sub.22 fatty acid amide derivatives of N-methyl glucamine or N-melhyl fructamine) requires an inexpensive source of such materials which have desirable low fatty acid levels, since such fatty acids (especially C.sub.14, and higher chain lengths) can substantially reduce sudsing. Indeed, the manufacturer of high sudsing, high cleaning dishwashing liquids which are formulated to contain calcium and/or magnesium cations is also especially concerned with having a source of surfactants which contain little or no nascent fatty acids, due to the prospective formation of "curd" by the reaction of such cations with fatty acids which may contaminate the formulations.
The present invention solves the problem of contamination by nascent sources of fatty acids associated with the manufacture of polyhydroxy fatty acid amides, and thereby affords access to a high quality supply of this class of surfactants.